ProgramNode(0...25)(
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    [CaseNode(0...25)(
       CallNode(5...6)(nil, nil, (5...6), nil, nil, nil, nil, 0, "a"),
       [WhenNode(8...15)(
          (8...12),
          [SplatNode(13...15)(
             (13...14),
             CallNode(14...15)(nil, nil, (14...15), nil, nil, nil, nil, 0, "b")
           )],
          nil
        )],
       nil,
       (0...4),
       (22...25)
     )]
  )
)
